Optimal pressure calibration method for heat pump system

Abstract

The invention discloses an optimal pressure calibration method for a heat pump system. The optimal pressure calibration method comprises an earlier-stage statistical method and a later-stage using method. The earlier-stage statistical method comprises the steps that 1, working condition boundary conditions are set; 2, compressor working condition parameters are set; step 3, acquiring output parameter information of the compressor; 4, the steps 1-3 are cycled, and an output matrix table is obtained under different working condition boundary conditions and compressor working condition parameters; 5, obtaining an MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table; according to the later use method, when the CO2 heat pump system pressure of the automobile is calibrated, the CO2 heat pump system calibration pressure of the automobile is obtained by checking the MAP table of the optimal pressure of the CO2 heat pump system based on the current parameters of the automobile. According to the method, the optimal pressure target can be found from the operation angle of the CO2 heat pump system, the actual operation state is controlled in combination with the target, and the optimal characteristics of the CO2 system are volatilized.

Description

Technical Field

[0001] The present invention relates to the field of automobile thermal management, and in particular to a CO2 heat pump system optimal pressure calibration method and system thereof in a new technology project. Background Art

[0002] Due to relevant laws and regulations and domestic carbon emission requirements, as well as good performance at low temperatures, CO2 refrigerant has a great market demand as an environmentally friendly refrigerant. CO2 refrigerant is a low-temperature refrigerant. Its physical properties determine that its operating cycle is a supercritical cycle. The temperature and pressure are separated in the high temperature and high pressure state. The control strategy of the actual system operation must be different from the control strategy of the medium-temperature refrigerant operation. The CO2 system has an optimal working pressure in actual operation. In order to ensure that the optimal characteristics of the CO2 system are fully utilized, finding the optimal pressure target value under each operating condition is the key to control.

[0003] The physical properties of CO2 refrigerant determine that its working state is in a supercritical state, and determine that its system working control method is different from that of traditional refrigerants. However, the current calibration of the thermal management system is not applicable to heat pump systems using CO2 refrigerants. For example, the public document with publication number CN115222097A, publication date 2022-10-21, and patent name "Calibration Method and Calibration Device for Electric Vehicle Thermal Management System" discloses that the calibration method includes: integrating CAN basic data into the integrated thermal management system, and the integrated thermal management system monitors the global variables of the vehicle status information in real time; the thermal management device performs thermal management on the functional unit to be calibrated according to a preset program, so that the functional unit to be calibrated reaches the target temperature; planning the driving route according to the requirements of different seasons and different working conditions, and executing the planned driving route. When the functional unit to be calibrated reaches the target temperature, the parameter value of the current thermal management device is calibrated when the heat generated by the thermal management device is equivalent to the actual heat generated.

[0004] The heat pump system using CO2 refrigerant has an optimal working pressure point in the supercritical state. Currently, there is a lack of a method to find the optimal pressure or optimal working point to ensure the operation of the CO2 system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to realize a method for calibrating a CO2 heat pump system so that the system can operate at the optimal working pressure curve in a supercritical state, ensure its optimal performance and energy efficiency in various operating states, and improve the comfort, economy, and reliability requirements of the entire thermal management system.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is: a method for calibrating the optimal pressure of a heat pump system:

[0007] Including early statistical methods and later usage methods:

[0008] The preliminary statistical methods include:

[0009] Step 1: Set the working boundary conditions;

[0010] Step 2: Set the compressor operating parameters;

[0011] Step 3, obtaining compressor output parameter information;

[0012] Step 4, looping steps 1-3, obtaining an output matrix table under different operating boundary conditions and compressor operating parameters;

[0013] Step 5: Obtain a MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table;

[0014] The later use method is to obtain the CO2 heat pump system calibration pressure of the vehicle by looking up the MAP table of the CO2 heat pump system optimal pressure based on the current parameters of the vehicle when the CO2 heat pump system pressure of the vehicle is calibrated.

[0015] The boundary condition setting dimensions of step 1 include HVAC air volume, HVAC inlet air temperature, ambient temperature, and Cond inlet air speed.

[0016] The step 1 obtains a working condition combination table with ambient temperature and Cond air inlet speed as the horizontal axis and HVAC air volume and HVAC air inlet temperature as the vertical axis, wherein each ambient temperature corresponds to several Cond air inlet speeds, and each HVAC air inlet temperature corresponds to several HVAC air volumes.

[0017] The step 2 is to set different operating conditions of the compressor under different boundary conditions of the step 1, including changing the speed of the compressor and changing the EXV opening of the compressor.

[0018] The compressor output parameters obtained in step 3 are based on the compressor parameter information under each fixed value condition determined in steps 1 and 2, including compressor exhaust pressure and exhaust temperature signals, compressor suction pressure and temperature signals, EVA outlet air temperature signal, EVA capacity, and compressor power consumption.

[0019] The output matrix table in step 4 uses the compressor speed and the variable compressor EXV opening as the horizontal axis of the table and the compressor output parameter information as the vertical axis to obtain different compressor output parameter information under different compressor speeds and variable compressor EXV openings.

[0020] In step 5, each grid in the operating condition combination table is used as an environmental benchmark, and each environmental benchmark obtains multiple output matrix tables. These output matrix tables are evaluated to obtain the optimal table for the environmental benchmark, which is used as the MAP table of the optimal pressure of the CO2 heat pump system for the environmental benchmark.

[0021] The later use method corresponds the ambient temperature and the current wind speed of the external air exchange cooler to the ambient temperature and Cond inlet wind speed of the working condition combination table, and corresponds the current HVAC inlet air volume and cabin return air temperature of the car to the HVAC air volume and HVAC inlet air temperature of the working condition combination table to obtain the environmental benchmark.

[0022] According to the optimal pressure MAP table of the CO2 heat pump system based on the current environment, the most ideal compressor speed and EXV2 control combination are selected, and the optimal calibration pressure of the corresponding heat pump system is obtained and executed.

[0023] The present invention can find the optimal pressure target from the perspective of the operation of the CO2 heat pump system, control the actual operating state in combination with the target, and exert the optimal characteristics of the CO2 system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following is a brief description of the contents expressed in each figure in the specification of the present invention:

[0025] Figure 1 Calculate boundary relationship graphs for testing and simulation;

[0026] Figure 2 Calculate the working condition combination table for testing and simulation;

[0027] Figure 3 Output matrix table for testing and simulation calculation;

[0028] Figure 4 The optimal pressure MAP table output by simulation calculation under example working condition 2; DETAILED DESCRIPTION

[0029] The following is a further detailed description of the specific implementation methods of the present invention, such as the shape, structure, relative position and connection relationship between the various components involved, the function and working principle of each part, the manufacturing process and operation method, etc., through the description of the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] like Figure 1 As shown in the figure, under the actual operating conditions of the CO2 system, during cooling, the high-temperature and high-pressure gas is discharged through the compressor, SOV2 is opened, and the air enters the external air cooler, and then flows into the evaporator through the expansion valve EXV1 to evaporate and absorb heat, and then returns to the compressor through SOV3 and AD; during heating, after the high-temperature and high-pressure gas leaves the compressor, SOV1 is opened, and the cold air enters the interior, passes through EXV3 and the evaporator, is throttled by EXV1, flows to the external air cooler through IHX to absorb heat, and then returns to the compressor through SOV4 and AD.

[0031] The present invention is a CO2 heat pump system optimal pressure calibration method. When leaving the factory, the vehicle needs to be calibrated and set (statisticed) to obtain the corresponding table. In the early stage of statistics,

[0032] First, set the different working condition boundaries of the external air cooler and the different working condition boundary conditions of the HVAC assembly. The boundary condition setting dimensions include HVAC air volume, HVAC inlet air temperature, ambient temperature, and Cond inlet air speed. The working condition combination table uses ambient temperature and Cond inlet air speed as the horizontal axis and HVAC air volume and HVAC inlet air temperature as the vertical axis. Each ambient temperature corresponds to several Cond inlet air speeds, and each HVAC inlet air temperature corresponds to several HVAC air volumes. Here, the ambient temperature is set with equally spaced point values. For example, a set of data is obtained every 5 degrees Celsius. When looking up the table, the closest parameter shall prevail. If the current temperature is between two temperatures, you can follow the settings. For example, when it is 37.5 degrees, it is exactly between 40 degrees and 35 degrees. At this time, the default query is 35 degrees data. Each ambient temperature corresponds to a different Cond inlet wind speed, and the Cond inlet wind speed is also set at intervals. For example, if the Cond inlet wind speed data is set to 1.8km / h, 2.5km / h, 3.0km / h, and 3.5km / h, then if 4 groups of ambient temperatures are set, there will be 16 columns of data; similarly, the HVAC inlet air temperature is also set at equally spaced point values, and each HVAC inlet air temperature is corresponding to a corresponding group of HVAC air volumes, so a working condition combination table is obtained, and each cell of the working condition combination table is used as the environmental benchmark;

[0033] Secondly, according to the different compressor speeds, different EXV openings are scanned, and different working conditions of the compressor are set under different boundary conditions in step 1, including changing the compressor speed and changing the compressor EXV opening; then, the compressor exhaust pressure and exhaust temperature signals, compressor suction pressure and temperature signals, compressor voltage and current signals, EVA outlet air temperature signals, etc. are collected to calculate the EVA capacity and the corresponding system COP value, and the output matrix table under different conditions is formed by combining the changing compressor speed and the changing compressor EXV opening; here it is necessary to determine the compressor parameter information under each environmental benchmark, including the compressor exhaust pressure and exhaust temperature signals, the compressor suction pressure and temperature signals, the EVA outlet air temperature signal, the EVA capacity, and the compressor power consumption.

[0034] The output matrix table uses the compressor speed and the variable compressor EXV opening as the horizontal axis of the table, and the compressor output parameter information as the vertical axis, to obtain different compressor output parameter information under different compressor speeds and variable compressor EXV openings. Therefore, there are as many sets of output matrix tables as there are environmental benchmarks, and each environmental benchmark obtains multiple output matrix tables. These output matrix tables are evaluated to obtain the optimal table for the environmental benchmark, which serves as the MAP table of the optimal pressure of the CO2 heat pump system for the environmental benchmark.

[0035] Finally, when in use, these tables are stored in the CO2 heat pump system of the car. During the car form process, when the CO2 heat pump system pressure is calibrated, the corresponding environmental benchmark is obtained based on the current parameters of the car, that is, the ambient temperature and the current wind speed of the external air exchange cooler correspond to the ambient temperature and Cond inlet wind speed of the working condition combination table, and the current HVAC inlet air volume and cabin return air temperature of the car correspond to the HVAC air volume and HVAC inlet air temperature of the working condition combination table to obtain the environmental benchmark. The calibrated pressure of the CO2 heat pump system of the car is obtained by checking the MAP table of the optimal pressure of the CO2 heat pump system.

[0036] The refrigerant is in a supercritical state in the external air cooler during cooling and in the internal air cooler during heating. The high pressure is generally around 110 Bar and the temperature is generally between 110 and 150 °C. In order to give full play to the advantages of CO2 in a supercritical state and adapt to the long-term operating pressure, temperature and other conditions that components such as compressors can withstand, the compressor limit values ​​for cooling and heating are proposed: exhaust pressure <120 bar, exhaust temperature <150 °C; suction pressure >10 bar; according to different usage environments or system operating boundaries, the required parameter performance values ​​obtained after operation are used to select appropriate operating control parameters, corresponding parameter boundaries and control and output objects.

[0037] In the actual driving process of the vehicle, the ambient temperature, vehicle speed and fan operation constitute the heat exchange environment of the external air cooler. Therefore, the ambient temperature and the current wind speed of the external air cooler are used as the working boundary of the outdoor air side. The boundary conditions of the heat exchanger in the vehicle are determined by the HVAC inlet air volume and the return air temperature in the cabin. Therefore, these two parameters are used as the working boundary. The working conditions for the test or simulation calculation are combined as shown in the attached figure. Figure 2 .

[0038] According to the operating limit requirements and Figure 1 The demand parameters are expressed in combination with Figure 2 The operating boundary of the compressor is tested or simulated to calculate the output at different compressor speeds and various openings of the EXV. Figure 3 ,in Figure 4 The table shows a set of output examples, which is actually an output matrix table; Figure 3 The output matrix table is used to select the wind side heat exchange capacity, outlet air temperature, compressor power consumption, and COP under various environmental conditions. Combined with the actual demand conditions under various environmental conditions (including the needs of cabin personnel and battery needs, or both), the most ideal compressor speed and EXV2 control combination under various environmental conditions are selected to form an overall control MAP to support actual calibration requirements and achieve control requirements.

[0039] The present invention seeks the optimal pressure target from the perspective of the operation of the CO2 heat pump system, combines the target with the actual operating state to give full play to the optimal characteristics of the CO2 system, and quickly finds the optimal working pressure curve of the CO2 heat pump system in the supercritical state to ensure its optimal performance and energy efficiency in various operating states, thereby improving the comfort, economy, and reliability requirements of the entire thermal management system.

[0040] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for calibrating optimal pressure of a heat pump system, characterized in that: Including early statistical methods and later usage methods: The preliminary statistical methods include: Step 1: Set the working boundary conditions; Step 2: Set the compressor operating parameters; Step 3, obtaining compressor output parameter information; Step 4, looping steps 1-3, obtaining an output matrix table under different operating boundary conditions and compressor operating parameters; Step 5: Obtain a MAP table of the optimal pressure of the CO2 heat pump system based on the obtained output matrix table; The later use method is to obtain the CO2 heat pump system calibration pressure of the vehicle by looking up the MAP table of the CO2 heat pump system optimal pressure based on the current parameters of the vehicle when the CO2 heat pump system pressure of the vehicle is calibrated.

2. The optimal pressure calibration method for a heat pump system according to claim 1, characterized in that: The boundary condition setting dimensions of step 1 include HVAC air volume, HVAC inlet air temperature, ambient temperature, and Cond inlet air speed.

3. The optimal pressure calibration method for a heat pump system according to claim 2, characterized in that: The step 1 obtains a working condition combination table with ambient temperature and Cond air inlet speed as the horizontal axis and HVAC air volume and HVAC air inlet temperature as the vertical axis, wherein each ambient temperature corresponds to several Cond air inlet speeds, and each HVAC air inlet temperature corresponds to several HVAC air volumes.

4. The optimal pressure calibration method for a heat pump system according to claim 3, characterized in that: The step 2 is to set different operating conditions of the compressor under different boundary conditions of the step 1, including changing the speed of the compressor and changing the EXV opening of the compressor.

5. The optimal pressure calibration method for a heat pump system according to claim 4, characterized in that: The compressor output parameters obtained in step 3 are based on the compressor parameter information under each fixed value condition determined in steps 1 and 2, including compressor exhaust pressure and exhaust temperature signals, compressor suction pressure and temperature signals, EVA outlet air temperature signal, EVA capacity, and compressor power consumption.

6. The optimal pressure calibration method for a heat pump system according to claim 5, characterized in that: The output matrix table in step 4 uses the compressor speed and the variable compressor EXV opening as the horizontal axis of the table and the compressor output parameter information as the vertical axis to obtain different compressor output parameter information under different compressor speeds and variable compressor EXV openings.

7. The optimal pressure calibration method for a heat pump system according to claim 6, characterized in that: In step 5, each grid in the operating condition combination table is used as an environmental benchmark, and each environmental benchmark obtains multiple output matrix tables. These output matrix tables are evaluated to obtain the optimal table for the environmental benchmark, which is used as the MAP table of the optimal pressure of the CO2 heat pump system for the environmental benchmark.

8. The optimal pressure calibration method for a heat pump system according to claim 7, characterized in that: The later use method corresponds the ambient temperature and the current wind speed of the external air exchange cooler to the ambient temperature and Cond inlet wind speed of the working condition combination table, and corresponds the current HVAC inlet air volume and cabin return air temperature of the car to the HVAC air volume and HVAC inlet air temperature of the working condition combination table to obtain the environmental benchmark.

9. The optimal pressure calibration method for a heat pump system according to claim 8, characterized in that: According to the optimal pressure MAP table of the CO2 heat pump system based on the current environment, the most ideal compressor speed and EXV2 control combination are selected, and the optimal calibration pressure of the corresponding heat pump system is obtained and executed.

Images